This invention relates to desiccant containers for use in air or fluid dryers of automotive air conditioning systems. More specifically, it relates to desiccant cartridge fiberglass filter and bead cage ends for desiccant retention.
Desiccants are commonly used in automotive air conditioning systems for dehydrating air and refrigerants. Desiccant particles are common in such systems because the high surface area to volume ratios of the particles facilitates their interaction with surrounding air or fluid. Since the desiccant particles must be held in the air or fluid stream and prevented from contaminating other parts of the system, the particles must be held in a container which is permeable to the air or fluid but impermeable to the particles. One form of dryer used in automotive air conditioning systems includes an elongated receiver or accumulator canister having inlet and outlet ports communicating with the interior of the canister. A desiccant container is positioned in the interior of the canister and allows for air and/or fluid through the desiccant material.
One form of package-type desiccant container for use in accumulator or receiver dryers is constructed from synthetic felted wool or polyester which is filled with desiccant and then sealed by stitching or fusing. One drawback to this form of package is that the felted bag may not conform to the shape of the canister so that air or fluid may bypass the desiccant. Another drawback is that the bag may be non-uniform in shape, thereby making automatic assembly of the dryer difficult.
If felted polyester is used as a less expensive substitute for felted wool, the seams of the bag may be formed by ultrasonic welding. Unfortunately, the reliability of such ultrasonic weld is questionable and the bag may open allowing absorbent material to escape from the bag and potentially contaminating the system. In addition, the felted polyester bag is vulnerable to burn-through when the dryer is welded shut.
In another proposed form of an accumulator or receiver dryer, the desiccant particles are trapped between a pair of grids or plates which are welded or pressed inside the canister. According to one embodiment, the desiccant is charged by pouring the desiccant particles into the canister once a first of the grids or plates is positioned. A pipe extends through holes in the grids or plates to exhaust dried air to an outlet port. A dryer of this form is likely to be difficult to assemble because the grids or plates must be slid into position and, in some cases, welded inside the canister. Further, since the desiccant particles are manually poured into the container, the desiccant must be pre-measured due to the difficulty of controlling the amount of desiccant poured into the canister based on visual observation alone. The pouring of the desiccant creates a risk of accidental contamination outside the accumulator since desiccant particles may fall into the pipe communicating with the outlet port. Nevertheless, the amount of desiccant poured into the canister may vary from canister to canister for at least the reasons mentioned above.
U.S. Pat. No. 5,522,204, the contents of which are hereby incorporated by reference, discloses a two-piece desiccant container which can be inserted into an accumulator or receiver dryer. This desiccant container includes a cup for holding particle desiccant, and a cap which is locked to the cup by an integral detent on an inner wall portion of the cup.
U.S. Pat. No. 5,529,203, the contents of which are hereby incorporated by reference, also discloses a two-piece desiccant container which can be inserted within an accumulator or receiver dryer. The desiccant container includes a cup for holding particle desiccant and a cap. The cap is designated for receipt in a chamber to cover the opening. In addition, the cap has a hole for receiving the inner wall portion of the cup. The cup includes a number of nib segments which are arranged into axially spaced nib groupings. The cap includes an edge portion which permits the cap to be retained between axially adjacent nib groups, thus retaining the cap within the cup in one of a number of axially spaced positions. The desiccant particles are either poured directly into the cup or into a felted bag which, in turn, is inserted into the cup before the desiccant container is inserted within the receiver dryer. It is important that desiccant not shift once the cap is locked into place. If there is not enough desiccant to fill the predetermined volume, or if the desiccant should settle over time, then the desiccant within the container will undesirably shift within the chamber.
Accordingly, there is a need in the art to provide a desiccant container which is simple to assemble with means for retaining a cap such that the container can prevent attrition of, and escape of, the desiccant particles while maintaining acceptable fluid flow characteristics and being capable of withstanding the temperature conditions and extreme environment within an automotive air conditioning system.